An intranetwork (intranet) may include a number of data centers. A data center is a facility that houses one or more computing systems for a business, industry, governmental entity, or other organization. Such computing systems may include, for example, one or more servers or server clusters that perform various functions for the organization.
Examples of such functions include hosting web sites, storing information, and providing processing for computing applications, among others. Other computing systems may be housed in a data center for performing other functions.
Information and application processing associated with a data center may be important to particular organizations. Such information and application processing may be associated with one or more stand alone servers and/or server clusters (these are generally referred to herein as “servers”).
Various efforts have been made to provide high availability servers. For example, some servers are provided with physical security such as housing the server in a data center in an inconspicuous location, providing restricted access to the server, providing the server with environmental isolation and control, and/or providing electrical power supply redundancy to the server. An element of security that has been added to data center design is to provide an organization with more than one physical data center (e.g., providing multiple data centers at different locations).
Providing “redundant” (also called “backup”) servers may provide an organization with the ability to protect server functionality against harmful factors that may otherwise create a single point of failure. For example, a single server may be vulnerable to physical failure (e.g., from terrorist activity, fire, earthquake, etc).
A single server and/or the applications hosted by the server may also be vulnerable to electronic failure (e.g., “hacker” activity or unplanned hardware failure events) such as viruses, broadcast storms, denial of service attacks, network device failures, storage device failures, and the like. Further, a single server associated with a data center may be vulnerable to electric and/or telecommunications failure of such a magnitude that hardware and software equipment internal to the data center may be unable to mitigate the failure.
Other failures reducing or eliminating the functionality of a single server are possible. In such instances, having additional servers, such as at separate geographic locations, may provide the organization with the ability to maintain server functionality after the loss of a single server.
A goal in providing a high availability intranet may be eliminating single points of failure. However, providing certain areas of redundancy in a network may create other issues such as broadcast stomis and/or “split-brain” problems.
A broadcast storm can, for example, be caused by network traffic that circulates through the network and generates response traffic from a number of computing devices on the network causing a flood of traffic that may prevent the network from being used for meaningful traffic if the storm is not stopped or prevented. Such situations may arise, for example, from having redundant links between two or more network devices that forward broadcasts such that each device may forward the broadcast traffic to the other in a loop.
A split-brain problem may exist, for example, when a redundant passive server is provided to host applications in the event an active server hosting the one or more applications fails. If a mechanism that allows the active and passive servers to determine whether the other server is functioning fails, both the active and the passive servers may operate on the premise that the other server is not functioning, thus providing two active servers where application hosting may be divided between the two such that the two active servers simultaneously attempt to access shared resources, among other functions they may perform in duplicate.